Non-invasive suture anchor and method

ABSTRACT

A non-invasive device for anchoring a suture includes a sheet to which a suture can be attached and an adhesive that can affix the sheet to bone. The method provides placing effective amount of an adhesive on a bone and attaching the suture to the adhesive and allowing the adhesive to set.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of International ApplicationNo. PCT/US2011/060956 filed on Nov. 16, 2011, which claims the benefitof Provisional U.S. Patent Application Ser. No. 61/416,406, filed onNov. 23, 2010, the entire contents of both are incorporated herein byreference.

REFERENCE REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

SEQUENTIAL LISTING

Not applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to suture anchors and more particularly to sutureanchors and methods of using suture anchors that can attach soft tissueto bone and are also minimally invasive to bone.

2. Description of the Background of the Invention

During various surgical procedures, it is often necessary to attach softtissues, like a ligament or tendon, to bone. Typically the suture isanchored in to the bone using a suture anchor that is drilled orsometimes punched or stapled into the bone. Sutures also can be anchoredby placing a suture into a predrilled hole in the bone that is alsofilled with an adhesive material such as disclosed in U.S. Pat. No.5,665,110.

For patients with compromised bone structure, such as elderly patients,that have ruptured a tendon or ligament, the poor quality of the bonestructure due to osteoporosis or osteopenia can limit the effectivenessof prior systems of anchoring sutures to bone. If the suture anchor issubject to being pulled out of the bone before the soft tissue has achance to fully heal there can be clinical failure of the procedure andthe patient must undergo a follow on procedure or suffer with decreasemobility or range of motion. Prior attempts to remedy this issue havefocused on using larger diameter anchors to increase the pull outresistance or other methods of fixation such as double row repairs whichrequire additional anchors or massive cuff stitching.

SUMMARY OF THE INVENTION

One embodiment of the present disclosure comprises a method of affixinga suture to bone in a minimally invasive manner that includes the stepsof applying an effective amount of an adhesive to the outer surface of abone, attaching a suture to the adhesive and allowing the adhesive toset.

A further embodiment of the present disclosure comprises a suture anchorthat can be adhesively attached to the surface of bone comprising arelatively flat sheet and a suture attached to the sheet.

A still further embodiment of the present disclosure comprises a kit forattaching a suture to bone that includes a suture and a calciumphosphate bone adhesive that when set has a separation force of greaterthan 30 N.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the top of one embodiment of the suture anchorof the present disclosure;

FIG. 2 is a plan view of the bottom of the embodiment of FIG. 1;

FIG. 3 is a plan view of the bottom of the embodiment of FIG. 1 showingan alternative embodiment;

FIG. 3 a is a side view of the embodiment of FIG. 1 showing the sutureanchor attached to bone;

FIG. 4 is a plan view of the top of a second embodiment of a sutureanchor;

FIG. 5 is a side view of the embodiment of FIG. 4;

FIG. 6 is a plan view of the bottom of a further alternative embodimentof the suture anchor of the present disclosure;

FIG. 6 a shows a side view of an alternate embodiment of FIG. 6;

FIG. 6 b show a side view of a further alternate embodiment of FIG. 6;

FIG. 7 is a view of a suture attached to bone using one embodiment ofthe method of the present disclosure;

FIGS. 7 a-c show alternate arrangements for the embodiment shown in FIG.7;

FIG. 7 d is an enlargement of a portion of the embodiment of FIG. 7 c toshow detail;

FIG. 8 is a partly broken away view of the embodiment of FIG. 7 takenalong line 8-8;

FIG. 9 is a view similar to FIG. 8 showing an alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, a suture anchor 20 has a relativelyflat sheet 22. Sheet 22 can be formed from a wide range of biocompatiblematerials including titanium, titanium alloys, ferrous alloys,cobalt-chromium alloys, degradable metals, biocompatible polymers,bioceramics, or composites of polymer and ceramics. Examples ofbiocompatible polymers include but are not limited to poly(ether-etherketone), poly (L-lactide), poly (D,L-lactide), polyglycolide,polycaprolactone, poly(tetramethylglycolic acid), poly(hydroxybutyrate),poly(hydroxyvalerate), poly(L-lactide-co-glycolide),poly(D,L-lactide-co-glycolide),poly(glycolide-co-trimethylenecarbonate),poly(glycolide-co-caprolactone), poly(dioxanone),poly(glycolide-co-dioxanone-co-trimethylene-carbonate),poly(glycolide-co-caprolactone-co-L-lactide-co-trimethylene-carbonate),poly(hydroxybutyrate-co-hydroxyvalerate), poly(methyl-methacrylate),poly(acrylates), polyamines, polyamides, polyimidazoles, polynitriles,poly(vinyl-pyrrolidone), collagen, silk and keratin, chitin, acombination thereof, or a copolymer thereof. The polymer structure canbe linear, block, branched, hyperbranched or star shaped polymers.Examples of bioceramics include but are not limited to hydroxyapatite,P-tricalcium phosphate, tetracalcium phosphate, biphasic calciumphosphate, nanocrystalline hydroxyapatite, bioactive glass, 45S5bioactive glass, titanium oxide, aluminum oxide. Composites may consistof any combination of any one or more of the above mentionedbiocompatible polymers with any one or more of the above mentionedbioceramics. Sheet 22 can be any suitable thickness, size or shape andin some embodiments sheet 22 can be sufficiently flexible or malleableto conform to the shape of the bone surface to which the suture anchor20 is to be affixed. Sheet 22 has at least 1 hole 24 passing throughsheet 22 so that a suture 26 can pass through these holes as shown. Eventhough 2 holes are shown in the figures, in some embodiments a singlehole may be all that is required. The only requirement for sheet 22 isthat sheet 22 be sufficiently strong or robust so that the suture 26will not rupture the area of sheet 22 between holes 24 at pressures thatsuture 26 will encounter during normal patient activity. Additionalholes 24 can be placed in sheet 22 and these holes will allow the suture26 to be place in different positions for different procedures. Also,these added holes 24 can also assist the formation of the bond of sheet22 to the bone formed by the adhesive as the adhesive can penetrate theholes 24 to further lock the sheet 22 in place and increase purchase orremoval force. In one embodiment, the sheet 22 has a size of 5 mm by 8mm, however larger or smaller sheets 22 can be used depending on theclinical need or the procedure.

The front and rear surfaces 28 of sheet 22 can be either smooth as shownin FIGS. 1 and 2 or as shown in FIG. 3, an alternative embodiment of asuture anchor 30 has a sheet 32 formed from similar materials to sheet22 but one or both of the surfaces of sheet 32 have grooves 36 or otherroughening the surface of the sheet 32 to further enhance adhesion ofthe sheet 32 to the bone by the adhesive. Sheet 32 also includes atleast two holes 34 that can be used to attach suture 26 to sheet 32.

As noted above, the sheet 22 or 32 is adhered to the underlying bone 38by an adhesive material 39 as shown in FIG. 3 a. The adhesive materials39 can be applied directly to the bone 38 or to the back of sheet 22 or32 prior to the plate 22 or 32 being placed near the bone 38. Also, asnoted above, the sheet 22 or 32 can be somewhat flexible or malleable sothat the sheet 22 can conform to the shape of the bone as shown in FIG.3 a.

Suitable adhesives include the calcium phosphate bone cements. It hasbeen found that tetra calcium phosphate (TTCP) has unusual propertiesnot shared by other calcium phosphate compositions. TTCP is the mostbasic of all the calcium phosphates; therefore, it readily reacts toacidic compounds. While other calcium phosphate compositions can be usedin addition to the TTCP, the compositions must include an effectiveamount of TTCP. The TTCP used in the present compositions can be made bya variety of methods. The TTCP can be 100% pure material or can includeother calcium and calcium phosphate materials as an impurity, e.g.α-TCP, CaO and/or HA.

A second component that can be included in the compositions is acompound that has the following formula;

where A is O, CH₂, or S; R is H, NH₂, NHCO(CH₂)_(t)CH₃ where t is 0 to2, NH(CH₂)_(x)CH₃ where x is 0 to 3, NR1R2 where R1 is (CH₂)_(y)CH₃ andR2 is (CH₂)_(y)CH₃ where y is 0 to 2, (CH₂)_(z)CH₃ where z is 0 to 3,where m is 0 to 1, and where n is 0 to 3. Preferred compounds are thosewhere A is O or CH₂, R is H or NH₂, m is 0 or 1 and n is 0 or 1. Themost preferred compound is phosphoserine that has the followingstructure;

The compounds that are structurally similar to phosphoserine, whichcontain the reactive phosphonate or phosphate, and which have COOHfunctional groups, are capable of interacting with the Ca⁺ within theTTCP to form a calcium based matrix and are referred to as compoundsstructurally similar to phosphoserine in this description. Thecombination of these functional groups plus the geometry such as thechain length between the phosphorous and the COOH are unique aspects tothe molecules which affect the level of adhesive bonding strength tosubstrate surfaces such as bone and metal.

The preferred compound that is structurally similar to phosphoserine isphosphoserine which may be any form of phosphoserine, including thephospho-D-serine, phospho-L-serine or the phospho-DL-serine forms may beused. The stereochemistry of the phosphoserine does not seem to have anyimpact on the properties of the compositions disclosed herein.

It has been found that when the quantity of compounds that arestructurally similar to phosphoserine is increased beyond about 10% w/wof the combination of the compound and the TTCP, more generally in therange of about 10% to about 90%, more typically in the range of 15% toabout 50%, or preferably from about 20% to about 40%, the tack andadhesion properties of the resulting compositions were significant. Atsuch levels, the influence of compounds that are structurally similar tophosphoserine extends beyond internal interaction with the cement, butalso extends to significant binding with the hydroxyapatite architectureand proteins of bone. At below about 10% by weight of the compoundstructurally similar to phosphoserine, the compositions do not have atacky state and these compositions do not have adhesive properties.

The compositions as described herein have many unique properties notfound in prior calcium phosphate compositions. One particularlyimportant property is that the compositions have a tacky stateimmediately subsequent to mixing with an aqueous medium. This tackproperty is retained for a number of minutes, sometimes up to 12 minutesdepending on the application requirement, typically up to about 4minutes, and preferably up to about 2 minutes, after mixing with theaqueous medium. The time of the tacky state is dependent on a number offactors including relative ratio of the components, the particle sizesof the component materials, the presence of additives and the like.During this time the compositions will adhere bone to bone and bone toother materials, often without the need for external clamping or otherapplication of pressure. The tacky state is not so aggressive that thecomposition will permanently affix the materials together at this pointin time. Rather the tacky state can allow the materials to be movedrelative to each other and also to be re-opposed without appreciableloss of ultimate cured strength. This is important in a medical settingso that the user can make sure the bone and the other material to beadhered to the bone are in the proper position relative to each other.

The tacky state is followed by a putty state. In the putty state, thetacky property has substantially disappeared and the compositions can beshaped or sculpted. In addition, during the putty state, the compositioncan be formed into shapes or used to fill voids in bone in a mannersimilar to putty. This putty state is retained for a number of minutes,sometimes up to 15 minutes depending on the application requirement,typically up to about 8 minutes, and preferably up to about 5 minutes,after mixing with the aqueous medium. Like the tacky states, the puttystate is dependant on a number of factors including the relative ratioof the components, the presence of additives, the particle size of thecomponents and the like. Because the items to be affixed can berepositioned during the tacky state or the compositions can be shapedduring the putty state, this combined time of the tacky state and theputty state is some times referred to as the working time. Typicalcompositions have a working time of up to 8 minutes from initial mixingand often the working time is up to about 5 minutes after which time thecompositions have sufficiently begun hardening that further manipulationwill result in degradation of ultimate strength of the bond.

After the putty state, the compositions harden like a cement to form asubstantially permanent bond between the materials. In the cement state,the composition hardens and the materials that have been affixed to eachother cannot be separated without the application of significant force.The compositions typically will begin to harden within about 8 minutes,and often within about 5 minutes, after mixing with the aqueous medium.The amount of time to reach the cement state is also dependant of thesame factors listed above.

A further important property of the compositions is that thesecompositions have significant coherency and integrity within a wetenvironment. In the medical field, this would include a surgical site, awound or similar situation where blood and other bodily fluids arepresent. The tacky state, the putty state and the cement state all occurin either a wet environment or in a dry environment. In order to get thedesirable properties, the user need not ensure that the application siteis clean and dry. In a wet environment, the compositions tend to remaintogether and the presence of the liquid does not significantly affectthe integrity of the composition or the ultimate strength properties.

As noted above, the compositions have a tacky state shortly afterinitial mixing. This tacky state enables two items, such as bone andanother material, to be held together by the composition itself, withoutthe need for external force, until the composition sets to the finalhardened cement state. The amount of force needed to remove two opposedpieces of material from each other is the separation strength. For thecomposition as described herein, these compositions have a separationstrength during the tacky state within the first 4 minutes andpreferably within the first 2 minutes after initial mixing from about 10kPa to about 250 kPa and preferably from about 50 kPa to about 150 kPa.For certain applications it may be useful to have a longer tack statewhereby certain compositions have a separation strength which continuesin this range for up to 12 minutes. This separation strength issufficiently high that the items to be joined need not be held togetherunless there is an apposing strength of the items greater than theseparation strength and also, the items can still be repositioned oreven reapposed without loss of ultimate bond strength.

Factors that may affect the length of the tacky state, the length of theputty states and the ultimate cure time, as well as strength propertiesof the compositions include: the percentage (w/w) TTCP and the compoundsthat are structurally similar to phosphoserine based solely on theweight of the TTCP and the compounds that are structurally similar tophosphoserine in the composition, the selection of the compounds thatare structurally similar to phosphoserine, the particle size of theTTCP, and the nature and quantity of any additives and/or fillers whichmay be combined to the composition to enhance the material properties.

The mean particle size of the TTCP should be below 1000 μm, preferably1-250 μm, most preferably 10-100 μm. As the mean particle size of theTTCP is reduced, the TTCP tends to dissolve too fast and thesecompositions may not be practical for all uses as disclosed herein. Onthe other hand if the TTCP has a mean particle size of greater thanabout 1000 μm, the intra-operative performance of the compositions maynot have the desired initial strength and be too slow to set. If alonger working time is desired, then TTCP with a larger mean particlesize can be used; however, if a shorter working time is desired, thenTTCP with a smaller mean particle sizes can be used. In certain useenvironments, compositions that have a multi-modal mean particle sizedistribution with, for example, one mode less then 50 μm and the othermode above 50 μm can provide unique properties such as a fast initialcure rate from the smaller mean particle size mode combined with higherintrinsic compression strength of the material from the larger meanparticle size mode. The TTCP may also be a solid mass or a coating ofTTCP on a substrate.

The aqueous based mixing media useful for combining the TTCP andcompound that is structurally similar to phosphoserine powders caninclude water, buffers such as sodium phosphate, saline, and blood basedproducts such as whole blood, plasma, platelet rich plasma, serum,and/or bone marrow aspirate. The blood based products are used with thegoal of achieving enhanced rate of bone healing and remodeling. It isalso possible to use the compositions without premixing with an aqueousmedium if the composition is to be used in a sufficiently wetenvironment that the aqueous medium can be absorbed from the in situsite. In this situation, the composition can be dusted on or other wiseapplied to the desired site and then mixed with the liquids that arealready present at the site.

Additives may enhance the material properties. These properties includethe handling, porosity, intrinsic material strength, & bone healing rate(osteogenic). Suitable additives include: alpha or beta tri-calciumphosphate (α-TCP or β-TCP), calcium sulfate, calcium silicate, calciumcarbonate, sodium bicarbonate, sodium chloride, potassium chlorideglycerol phosphate disodium, amino acids such as serine, excess amountsof phosphoserine, polyols (such as glycerol, mannitol, sorbitol,trehalose, lactose, & sucrose), silk, keratin (primarily found in humanhair), autologous bone powder or chips, demineralized bone powder orchips, collagen, various biodegradable polymers such as poly ethyleneglycol (PEG), poly lactic acid (PLLA), poly glycolic acid (PGA), andcopolymers of lactic and glycolic acid (PLGA), further includingbiodegradable block polymers such as poly lactic acid(PLLA)-polyethylene glycol (PEG)-poly lactic acid (PLLA) block polymer,BMP7, stem cells, parathyroid hormone (PTH), bisphosphonates, andmixtures thereof. In addition, other additives and/or fillers could beincorporated which offer surgical visual aids & anti-infectiveproperties.

While not wishing to be bound by theory, compositions of the presentdisclosure are believed to function as follows: the TTCP, which is basicin nature, reacts with the compound that is structurally similar tophosphoserine, which is acidic in nature, upon mixing with the aqueousmedium and forms a hardened, layered structure upon curing. Thisreaction is exothermic; the degree of exothermic activity depends on anumber of factors including the volume of the composition. The low pHnature of the compounds that are structurally similar to phosphoserineenable the hydroxyl of phosphate or phosphonate and COOH functionalgroup to bond through ionic interaction with the calcium ions fromwithin the TTCP. This resulting reactive intermediate continues acascade of ionic interactions with calcium and phosphate ions within theTTCP or HA on the bone surface or any other metal ions of the metalimplants. This series of interactions provides transient material havingthe tacky properties while curing and the adhesion strength thatincreases upon cure.

The compositions when mixed with aqueous medium typically have a creamyor a tacky paste consistency initially. Also, the mixing of thecompositions with the aqueous medium does not require a high level offorce or shear and simple hand mixing, such as with a spatula, issufficient in most instances. It is envisioned that the presentcompositions may be applied via injection through a syringe or othersuitable pressurized implement, applied with a spatula, and as otherwisedesirable by a user. The creamy or tacky viscosity allows forapplication of the composition to the defect site for a defined periodof time. The compositions allow the bone to be repositioned severaltimes within 4 minutes and preferably within 2 minutes without losingtack properties. If the compositions need to be injected through asyringe or cannula, the viscosity of the composition during the workingtime can be important. For these situations, viscosities of thecompositions herein should be preferably below about 150 centipoise.

Still further embodiments have a consistency similar to putty. Thesecompositions hold their cohesive, tacky, and sculpting properties over alonger period of time even when subjected to a wet field. Thecompositions have working time for sculpting sometimes up to 15 minutesdepending on the application requirement, typically up to about 8minutes, and preferably up to about 5 minutes, after mixing with theaqueous medium. Formulations with an increased amount of compound thatis structurally similar to phosphoserine greater than 25% w/w orincreased TTCP mean particle size greater than about 250 microns tend tohave longer working times and seem to be suitable for use in situationswhere the putty will fill defects in structures that are well supportedby surrounding bone. In these situations the putty does not need toharden as fast provided it maintains its cohesive properties in the wetfield. Another property of the compositions is that the compositionswill adhere to themselves as well as to an external surface such asbone. This is useful in situations where a shape is formed during theputty state and this shape can then adhere to bone. Also, in someinstances a user may apply a mass of the composition to a bone or othersurface and then shape the composition into the final desired shapeduring the working time of the composition.

In addition other suitable adhesives include polymethyl methacrylatebased adhesives, collagen based adhesives, fibrin based adhesives,hyaluronic acid based adhesives, gelatin based adhesives and PEG basedhydrogel adhesives.

An important property of the adhesive is the separation strength asdescribed above. Suitable adhesives have separation strength of at leastabout 30 N and preferably have a strength of between about 80 and about180 N. Particularly preferred adhesives include those that incorporatephosphoserine (OPLS), TTCP and other components such as PLGA (poly(lactic/glycolic acid)) fibers of various ratios of lactic and glycolicacid.

Fibers can be used in the adhesive composition to increase the materialintrinsic strength. An important aspect for chemical ion-dipole adhesionof these fibers is the size and/or surface area. The size or surfacearea can be defined by the aspect ratio (length:diameter). The preferredaspect ratio is from 2:1 to 50:1; more preferable from 10:1 to 35:1. Theoverall length of the fiber can be up to 5 mm; however, since thematerial could be used as bone to bone adhesive, the length of the fibermay be more appropriate at lengths that are less than this. The fibermay be any type of fiber that is suitable for use in a surgical setting.Examples include copolymers of lactic acid and glycolic acid with alactic acid glycolic acid ratio of between 5:95 and 70:30. Otherexamples include silk, keratin, collagen, autologous bone powder orchips, demineralized bone powder or chips, calcium silicate, calciumsulfate, biodegradable polymers (such as PLLA, PGA, PLGA) orbiodegradable block polymers (such as PLLA-PEG-PLLA), also granules madefrom calcium sulphate, α-TCP, β-TCP or hybrids thereof.

Examples of suitable adhesives are shown below in table 1.

TABLE 1 Formulation Test Configuration Failure Load 1A TTCP = 400 mg,Titanium plate on 141 N OPLS = 330 mg cortical bone PLGA fibers = 62.5mg Water = 165 microliters 1B TTCP = 400 mg, Titanium plate on 165 NOPLS = 400 mg cortical bone PLGA fibers = 62.5 mg Water = 180microliters 1C TTCP = 400 mg, Suture on cortical  76 N OPLS = 330 mgbone PLGA fibers = 62.5 mg Water = 165 microliters Note: PLGA Fibers = 4mm length, 200 micron diameter, Lactic: Glycolic ratio of 10:90

The amount of adhesive that is used is not particularly important solong as sufficient adhesive is used to form a strong enough bond betweenthe sheet 22 and the bone to hold the suture 26 in place and prevent thesuture anchor 20 from moving while the patient undergoes normalactivity. Typically sufficient adhesive is used so that it is notnecessary to form a groove between the holes 24 to form a relief areafor the suture 26. The suture 26 will press into the adhesive that isplaced between the sheet 22 and the bone and form a cohesive bond.

Because the suture anchor 20 is attached to the bone by use of anadhesive, there is minimal invasion of bone structure. This can beparticularly advantageous in situations where the patient has bones thatare compromised in some fashion due to age or medical condition. Evenfor patients with normal bone density, the use of a non-invasiveattachment method and device for sutures reduces the risk of postprocedure complications. As will be discussed hereinafter, certainembodiments of the present disclosure may minimally invade the outersurface of the bone but even these minimal invasions provide significantadvantages for patients with compromised bone structure and density andfor minimizing post procedure complications.

Referring to FIGS. 4 and 5, a suture anchor 40 has a sheet 42. On thetop surface of sheet 42 is an eyelet 44 that has an opening 48 thoughwhich a suture 26 can pass. The sheet 42 can be formed from any of thesame materials as discussed above and eyelet 44 has the advantage thatthe suture 46 can be attached after the suture anchor is affixed to thebone. Typically the suture 46 will be tied to eyelet 44 prior to beingused to adhere the soft tissue in position next to the bone.

FIG. 6 shows a bottom view of a suture anchor 50 that has a sheet 52with at least two holes 54 through sheet 52. The bottom surface of sheet52 has a series of protrusions 56 that in one embodiment have beenpunched through sheet 52. Protrusions 56 extend downward from the bottomsurface of sheet 52 and it is preferred that the size of the protrusionswill extend only into the adhesive that is placed between suture anchor50 and not into the surface of the bone. In a further embodiment, theprotrusions 56 are larger, and the protrusions 56 can penetrate a shortdistance into the outer surface of the bone. In this embodiment, somepressure or impact will be needed to seat the protrusions 56 into thebone. This can be done in any conventional manner. Although FIG. 6 showsthe protrusions placed downwards toward the bone, the structure can alsobe installed with the protrusions 56 facing upwards away from the bone.In this case, the adhesive will also be placed over plate 52 as well asbetween the plate 52 and the bone.

FIG. 6 a shows a further embodiment where the sheet 52 has protrusions56 extending downward and protrusions 57 extending upward. In thisembodiment, the size of protrusions 56 and 57 are similar to thosedescribed relative to FIG. 6. FIG. 6 b shows a still further embodimentwhere the sheet 52 has rectangular protrusions 58 extending downward andrectangular protrusions 59 extending upward. As shown the protrusions56, 57, 58, and 59 can angle toward the suture 26 so that theprotrusions will further grab the adhesive as tension is placed on thesuture 26.

FIGS. 7 and 8 show a further embodiment of the method of the presentdisclosure. In the embodiment shown in FIGS. 7 and 8, no separate sutureanchor is used. Instead, the bone 60 will have an area of adhesive 62placed on the bone 60. Sufficient adhesive 62 is used to create a largeenough area to securely hold suture 64. In some embodiments, the suture64 is either looped to form a loop 66 or knotted to increase the surfacearea contact between the adhesive 62 and the suture 64. In anotherembodiment as shown in FIG. 7 a, at least one end of the suture 64 isbraided such that it forms a net 68 to create a larger surface area. Inaddition to the net shown, other braided shapes can also be used tocreate a large surface area. Non-limiting examples include a mesh area68 a or a straight braided area 68 b as shown in FIGS. 7 b and 7 c. FIG.7 d is an enlargement of the braided areas of FIG. 7 c. Although FIG. 7c shows the braiding covering the entire circular area, it also possiblethat the braided area is only around the circumference of the area andthat the center portion is left open.

One advantage of this particular method is that less foreign material isintroduced into the body as part of the procedure because no plate isused. Typically about 0.5 g grams of adhesive 62 have been found to forma suitable bond between the bone 60 and the suture 64. The amount ofadhesive 64 used should be large enough to cover the suture 64 and holdit in place against the bone 60 but small enough so that the adhesive 62will set quickly. The exact amount of adhesive used is not important solong as sufficient adhesive 62 is used to secure the suture 64 to thebone.

The amount of time needed for the adhesive to set to the requiredseparation strength will depend in part on the particular adhesiveformulation used. Typically, the adhesive should set sufficientlyquickly so that the surgeon will not have to wait to attach the softtissue to the bone, often less than 10 minutes. It is recognized thatthe adhesive may set initially to a strength level sufficient to enablethe surgeon to suture to soft tissue to the bone and that the adhesivewill continue to set over time until the adhesive reaches its maximumstrength. For most adhesives that are suitable for use in the presentdisclosure, within 30 minutes the adhesive will set to a strength of atleast 90% of the final strength.

In FIG. 9 one further embodiment of the method of the present disclosureis illustrated. In this embodiment a sheet 70 is placed on top of theadhesive 62 that already has the suture 64 placed in the adhesive 62.The sheet 70 will protect the adhesive 62 and provide added surface areafor the adhesive 62 to adhere. By increasing the surface area, thisincreases the purchase of the resulting bond and makes the suture 64even more secure.

Typically, the components will be provided to the end user as a kit thatincludes adhesive premix, adhesive liquid, and an anchor sheet. In someembodiments, the sutures can also be provided in the same kit or becauseof the varying need for different suture sizes, the sutures can beprovided separately.

INDUSTRIAL APPLICABILITY

Numerous modifications to the present invention will be apparent tothose skilled in the art in view of the foregoing description.Accordingly, this description is to be construed as illustrative onlyand is presented for the purpose of enabling those skilled in the art tomake and use the invention and to teach the best mode of carrying outsame. The exclusive rights to all modifications which come within thescope of the appended claims are reserved.

We claim:
 1. A method of affixing a suture to bone in a minimallyinvasive manner comprising the steps of applying an effective amount ofan adhesive to the surface of a bone, attaching a suture to the adhesiveand allowing the adhesive to set.
 2. The method of claim 1, wherein theadhesive when set has a separation force of greater than or equal toabout 30 N.
 3. The method of claim 1, wherein the adhesive comprises,tetracalcium phosphate, phosphoserine and water.
 4. The method of claim3, further comprising, prior to the applying step, the step of mixingthe effective amount of tetracalcium phosphate, phosphoserine with waterto create the adhesive; wherein the adhesive has a tack state for up toabout 12 minutes after the tetracalcium phosphate and phosphoserine aremixed with the water, has a separation strength in the range of about 10kPa to about 250 kPa during the tack state, has a putty state for up toabout 15 minutes after the tetracalcium phosphate and phosphoserine aremixed with the aqueous medium, and an adhesive strength upon curing ofgreater than 250 kPa.
 5. The method of claim 3, wherein the adhesivefurther includes a fiber.
 6. The method of claim 1, wherein the sutureis threaded through a sheet and the sheet is adhesively bonded to thebone.
 7. A suture anchor that can be adhesively attached to the surfaceof bone comprising a relatively flat sheet and a suture attached to thesheet.
 8. The suture anchor of claim 7, wherein the sheet has one sidethat is roughened.
 9. The suture anchor of claim 7, wherein the sheethas protrusions extending from one side of the sheet.
 10. The sutureanchor of claim 9, at least one protrusion extends into the adhesive.11. The suture anchor of claim 9, wherein the at least one protrusionextends upward, and wherein additional adhesive is placed atop thesheet.
 12. The suture anchor of claim 9, wherein the at least oneprotrusion has a pointed shape.
 13. The suture anchor of claim 9,wherein the at least one protrusion has a rectangular shape.
 14. Thesuture anchor of claim 7, wherein the sheet comprises a materialselected from the following group: titanium, titanium alloys, ferrousalloys, cobalt-chromium alloys, degradable metals, biocompatiblepolymers, bioceramics, or composites of polymers and ceramics.
 15. Thesuture anchor of claim 7, wherein the sheet has an opening.
 16. Thesuture anchor of claim 15, wherein the opening comprises at least oneeyelet that extends from the top of the sheet.
 17. The suture anchor ofclaim 7, wherein the sheet has a smooth surface.
 18. A kit for attachinga suture to bone comprising a suture and a calcium phosphate boneadhesive that when set has a separation force of greater than, or equalto, about 30 N.
 19. The kit of claim 18 wherein the calcium phosphateadhesive comprises, tetracalcium phosphate, phosphoserine and water. 20.The kit of claim 19 wherein the adhesive further includes a fiber.